1. Field of the Invention
The present invention relates to a printing apparatus such as of a thermal transfer type, designed for use on an information processing apparatus and a communication apparatus. More particularly, it relates to a structure for deciding which portion of an ink sheet is used to print the ink sheet on a sheet of record paper in a printing system that rewinds the ink sheet in order to use the ink sheet a number of times.
2. Description of the Related Art
A thermal transfer printing system in which heat dissipated by a thermal head transfers ink of an ink sheet to a sheet of record paper in order to print the ink sheet on the sheet of record paper is well known. This art is in widespread use on printing apparatus such as a facsimile telegraph and a word processor. Although a one-time ink sheet printable single time prevails as an ink sheet employed in the printing apparatus, an ink sheet printable several times becomes even more popular.
Japanese Unexamined Patent Publication JP-A 59-207276 (1984) discloses a first prior art that copes with a one-time ribbon used on a serial thermal transfer printer. More specifically, a previously print area of the ribbon is compared with an area of the ribbon scheduled for printing, and the ink ribbon is rewound by one row when no overlap occurs between the compared two areas as mentioned above.
Japanese Unexamined Patent Publication JP-A 4-128053 (1992) discloses a second prior art that takes care of a multi-strike ink ribbon (an ink ribbon printable several times). More specifically, the number of times of use of a ribbon cassette is recorded, and pressure on a printing head is controlled in dependence upon the recorded number of times of use.
Japanese Unexamined Patent Publication JP-A 5-147242 (1993) discloses a third prior art in a thermal transfer printing apparatus that employs a multi-pass ink ribbon. More specifically, a temperature table for application on a thermal head is selectively used according to an ink ratio achieved until previous printing.
Japanese Unexamined Patent Publication JP-A 5-147296 (1993) discloses a fourth prior art in which an accumulated ratio of ink on a ribbon surface until previous printing is calculated, and an unused surface of the ink ribbon is used to practice the next printing when the accumulated ink ratio exceeds a certain level of ratio.
Even with the use of a multi-pass ink sheet or an ink sheet printable several times at the same position of the ink sheet, transfer printing is usually conducted a limited number of times. An increased number of times of transfer inevitably degrade printing quality in stages. Accordingly, the ink sheet is preferably subjected to uniform printing and ink transfer. When the ink sheet at first used is rewound for re-use, then an error in traveling of a crimped ink sheet caused by printing makes it difficult to expect that each portion of the ink sheet would be returned to the same position precisely.
There has been a need for a method for equalizing a consumption amount of ink on the ink sheet. In the fourth prior art (JP-A 5-147296) as previously discussed, the ink sheet is rewound each time when a page is printed, and a comparison is made between a previously printed bit map and a bit map to be now printed. In view of an error in traveling of the ink sheet, it would be very difficult to virtually employ a method for determining the number of times of printing according to a printing overlap per bit unit. Alternatively, the number of times of printing is determined from an accumulated ink ratio. When it is determined simply from the accumulated ink ratio at the entire print area on a page how the ink sheet is used, then the ink sheet ends up with inefficient use because there are found an area heavily worn out by printing and having a partially increased ratio of accumulated ink and a virtually non-print area that is excluded from the entire accumulated ink ratio.
An object of the invention is to provide an ink sheet type-printing apparatus designed to efficiently use an ink sheet while allowing an invariable level of printed image quality to be maintained.
Embodiments of the invention will now be summarized. In an information-processing apparatus and a communication apparatus, in which a recording method is employed for using a rewound ink sheet at least two times in a thermal transfer printing system that thermally transfers ink from the ink sheet onto a sheet of record paper, the thermal transfer printing system being used in a printing apparatus that is incorporated in the information-processing apparatus and the communication apparatus such as a facsimile telegraph and a Japanese language version of a word processor, the ink sheet is divided into several blocks in a virtual manner; first accumulated printing ratio xcex71 for each of the blocks is stored, which can also be called a ratio of dots already printed; second accumulated printing ratio xcex72 for each of the blocks according to an image scheduled for printing is calculated; calculated second ratio xcex72 is compared with stored predetermined value xcex70 of the ink sheet; and, print areas R1 to Rp are decided without the use of any print area having an increased consumption amount of ink, so as to average a total of evaluation values G for print areas R1 to Rp including the blocks.
The ink sheet is partitioned into a plurality of blocks in a virtual manner as large as compensating an error in which the ink sheet is traveled in a sub-scanning direction thereof. First and second accumulated printing ratios xcex71, xcex72 of the ink sheet are determined for each of the partitioned blocks. Evaluation value G is determined from first and second accumulated printing ratios xcex71, xcex72 for each of the print areas. Print areas of the ink sheet, which are scheduled for printing, are decided to provide an average amount of ink used on the entire ink sheet. As a result, the ink sheet can economically be used. A reduced error in traveling of the ink sheet allows the ink sheet to be used more economically.
The invention provides an ink sheet type-printing apparatus designed to use an ink sheet in recording on a sheet of record paper a number of times at a same position thereof, comprising:
moving means for permitting the ink sheet to be moved in a sub-scanning direction of thereof;
first calculating means for dividing the ink sheet in a virtual manner into a plurality of blocks in both a main scanning direction of the ink sheet and the sub-scanning direction thereof, and further for calculating accumulated printing ratios xcex71, xcex72 for each of the blocks, which correspond to amounts of ink to be consumed for printing;
second calculating means in response to an output from the first calculating means, for calculating an evaluation value for each of a plurality of print areas different in the sub-scanning direction of the ink sheet,
the evaluation value being related to accumulated printing ratios xcex71, xcex72; and,
print area-deciding means in response to an output from the second calculating means, for deciding a print area of the ink sheet to be used, according to the evaluation value, and for forcing the moving means to move the ink sheet in the sub-scanning direction of the ink sheet in order to carry out printing on a sheet of record paper using the decided print area of the ink sheet.
According to the invention, the first calculating means calculates accumulated printing ratios xcex71, xcex72 for each of the blocks of the ink sheet, while the second calculating means calculates evaluation value G for each of print areas R1 to Rp according to accumulated printing ratios xcex71, xcex72. Print areas R1 to Rp are displaced in the sub-scanning direction of the ink sheet. The print area-first accumulated printing ratio xcex71 for each of the blocks of the ink sheet, which is obtained after the ink sheet is printed, and the second calculating means calculates evaluation value related to second accumulated printing ratio xcex72.
According to the invention, the first calculating means calculates second accumulated printing ratio xcex72 according to an image scheduled for printing, using first accumulated printing ratio xcex71 for each of the blocks of the ink sheet, which is obtained after the ink sheet is printed, while evaluation value G is calculated using second accumulated printing ratio xcex72. As a result, precise evaluation value G for the image scheduled for printing is achievable.
According to the invention, in order to obtain evaluation value G for each of the print areas, second accumulated printing ratio xcex72 is calculated according to an image scheduled for printing, using first accumulated printing ratio xcex71 that is obtained after the ink sheet is printed. As a result, a proper print area is decided before the scheduled printing of the image is practiced, and the ink sheet is efficiently usable, resulting in improved printed image quality.
In the invention it is preferable that the print area-deciding means includes: deciding means decides a print area of the ink sheet to be printed onto a sheet of record paper, and then drives the moving means to move the ink sheet in the sub-scanning direction thereof in order to permit the decided print area to be used for printing. As a result, the ink sheet can be used a number of times at the same position thereof, and the ink sheet can efficiently be used, with a printed image quality maintained. This feature avoids wasting the ink sheet.
According to such an aspect of the invention, accumulated printing ratios xcex71, xcex72 are calculated for each of the blocks of the ink sheet. The blocks are divided in a virtual manner in the main scanning and sub-scanning directions of the ink sheet. The evaluation value is calculated for each of the print areas of the ink sheet in order to decide a print area to be used for printing. As a result, sharp printing is achievable while an image printed in the decided print area has a certain level of quality maintained. In addition, the ink sheet can efficiently be used because the above feature eliminates waste such that the ink sheet having still printable areas is discarded.
In the invention it is preferable that the first calculating means calculates second accumulated printing ratio xcex72 for each of the blocks of the ink sheet, responsive to the printing of an image to be printed, using
accumulated printing ratio-comparing means for comparing second accumulated printing ratio xcex72 for each of the blocks in each of the print areas with predetermined value xcex70 in order to determine whether the former xcex72 is equal to or less than the latter xcex70; and,
comparison-deciding means in response to an output from the accumulated printing ratio-comparing means, for deciding that any print area consisting of only blocks that have second accumulated printing ratio xcex72 equal to or less than predetermined xcex70 is used for printing.
In the invention it is preferable that the comparison-deciding means decides that from among a plurality of print areas consisting of only blocks having second accumulated printing ratio xcex72 equal to or less than predetermined xcex70, any print area having evaluation values related to accumulated printing ratios xcex71, xcex72 that correspond to a small consumption amount of ink is used for printing.
According to the invention, it is decided that print areas having second accumulated printing ratios xcex72 equal to or less than predetermined xcex70 for all of the blocks are used for printing. As a result, a sharp image can be printed throughout the print area.
From among a plurality of print areas consisting of only blocks that have second accumulated printing ratio xcex72 equal to or less than predetermined xcex70, any print area is used for printing in which evaluation value G for the print area is a value corresponding to accumulated printing ratios xcex71, xcex72 for the block having a small consumption amount of ink. As a result, the evaluation values G for the print areas to be used for printing is averaged, and the ink sheet can efficiently be used.
According to such a further aspect of the invention, any print area is used for printing, which consists of only blocks having second accumulated printing ratio xcex72 equal to or less than predetermined xcex70. As a result, the quality of printed images can be improved without being degraded.
According to the invention, from among a plurality of print areas, any printing area is used for printing, which has a value that is expressed by an evaluation value for such a print area, and further which corresponds to accumulated printing ratios xcex71, xcex72 having a small consumption amount of ink. As a result, improvements in printed image quality are achievable, and the evaluation values for the print areas are averaged, thereby allowing the entire ink sheet to be efficiently used. This feature avoids wasting the ink sheet.
In the invention it is preferable that the ink sheet is divided into a plural number q of groups in the sub-scanning direction of the ink sheet, each of the groups including a plural number p of print areas that are arranged respectively offset next to one another in the sub-scanning direction of the ink sheet, and wherein the comparison-deciding means decides that, when the print area to be used for printing is absent in a group, the print area to be used for printing in the other groups is used for printing.
According to the invention, the ink sheet, formed into a relatively long, roll-like shape, is divided into a plural number q of groups D0 to D(qxe2x88x921) in a longitudinal direction or the sub-scanning direction of the ink sheet. In each of the groups, a plural number p of print areas is displaced in the sub-scanning direction of the ink sheet. When second accumulated printing ratio xcex72 for each of the blocks in all of the print areas in each of the groups exceeds xcex70 to a degree that a consumption amount of ink in the group degrades printed image quality, or when any print area to be used for printing is absent in a group, then the comparison-deciding means decides to use a new print area to be used for printing in the other groups.
As a result, the ink sheet can efficiently be used for each of the groups. Such grouping eliminates the need for the moving means to move the ink sheet by a long distance in order to set a print area to be used for printing. Consequently, movement of the ink sheet can smoothly be set in a reduced time.
According to the invention, the print area to be used for printing is decided for each of the groups in the ink sheet in the sub-scanning direction thereof. When any print area suitable for printing is absent in any group, then new print area in the other groups is decided to use. As a result, the moving means moves the ink sheet by a shorter distance, and is allowed to smoothly move the ink sheet.
In the invention it is preferable that length LB2 of the block in the sub-scanning direction of the ink sheet is set to be equal to or greater than an error xcex94LB in traveling of the ink sheet.
Furthermore, in the invention it is preferable that the ink sheet has detected portions spaced apart from each other by a distance LB1 in the sub-scanning direction of the ink sheet, and the moving means includes detecting means for detecting the detected portions of the ink sheet in order to detect a position in the sub-scanning direction of the ink sheet, and movement control means in response to an output from the detecting means, for permitting the decided print area of the ink sheet to be moved to a position at which the ink sheet is printed on a sheet of record paper.
According to the invention, when the ink sheet is moved in the sub-scanning direction thereof for positioning, then predetermined blocks are used for printing, even with the presence of an error in traveling in the sub-scanning direction of the ink sheet. As a result, a certain level of printed image quality is maintained. Similarly, such blocking maintains an invariable level of printed image quality, even with the presence of an error in traveling in the main scanning direction of the ink sheet.
In order to provide accurate positioning of the ink Z7 sheet, the ink sheet is formed with the detected portions 42 such as marks. The detecting means detects the detected portions of the ink sheet, and then calculates a position in the sub-scanning direction of the ink sheet in order to detect such a position of the ink sheet. The movement control means provides accurate positioning of the ink sheet at a desired position in the sub-scanning direction of the ink sheet. The spacing LB1 of the detected portions in the sub-scanning direction of the ink sheet and the length LB2 of the block in the sub-scanning direction of the ink sheet may be set to be equal to or greater than error xcex94LB in traveling in the sub-scanning direction of the ink sheet (LB1xe2x89xa7xcex94LB, LB2xe2x89xa7xcex94LB) in order to further improve the accuracy of positioning.
Although the ink sheet can be of a thermal transfer type, the ink sheet may be struck by distal ends of needles in order to print the ink sheet on a sheet of record paper. Electromagnetic forces per dot drive the needles. Other structures may also be acceptable.
According to the invention, the print areas are precisely positioned irrespective of an error in traveling of the ink sheet caused by crimping of the ink sheet. As a result, printed image quality can be improved.